Device for efficient mixing of laminar, low-velocity fluids

ABSTRACT

A gas delivery system and method for delivering reactants such as a first gas through a first conduit and a second gas through at least one second conduit, for example, through a plurality of second conduits. The plurality of second conduits may each have a length, wherein at least a portion of the length is entirely disposed within the first conduit. In an implementation, the first conduit may deliver carbon monoxide and the one or more second conduits may deliver carbon monoxide doped with a catalyst such as iron pentacarbonyl. The first and second gases may be introduced into a reaction vessel such as a reactor chamber and used to form carbon nanotubes.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of, and claims priority to, U.S. patentapplication Ser. No. 15/373,521, filed Dec. 9, 2016, now allowed, thedisclosure of which is hereby incorporated herein by reference in itsentirety.

TECHNICAL FIELD

The present teachings relate to the formation of a material such as aplurality of carbon nanotubes within a chamber of a reactor and, moreparticularly, to the introduction or delivery of two or more fluidreactants such as two or more reactant gases into the reactor chamber

BACKGROUND

The utility of carbon nanotubes has been demonstrated in a wide range ofindustries such as aerospace, medicine, transportation, and many others.However, forming high-quality carbon nanotubes in large quantities,particularly single-walled carbon nanotubes, has proved difficult.

A new method and apparatus for forming carbon nanotubes, for example,high-quality single-walled carbon nanotubes in quantity, would be awelcome addition to the art.

SUMMARY

The following presents a simplified summary in order to provide a basicunderstanding of some aspects of one or more implementations of thepresent teachings. This summary is not an extensive overview, nor is itintended to identify key or critical elements of the present teachings,nor to delineate the scope of the disclosure. Rather, its primarypurpose is merely to present one or more concepts in simplified form asa prelude to the detailed description presented later.

In an implementation, a gas delivery system includes a first conduithaving a first end and a second end, wherein the first end of the firstconduit is attached to a first gas source. The gas delivery systemfurther includes a second conduit having a first end and a second end.The first end of the second conduit is attached to a second gas source.The second conduit has a length and is positioned entirely within aninterior of the first conduit over at least a portion of the length. Thegas delivery system also includes a gas delivery port that includes thesecond end of the first conduit and the second end of the secondconduit. The gas delivery port is configured to deliver a first gaswithin the first gas source through the first conduit into a reactorchamber and a second gas within the second gas source through the secondconduit to the reactor chamber.

Optionally, the gas delivery system can further include a plurality ofsecond conduits each having a length, and the length of each secondconduit is positioned entirely within the interior of the first conduitover at least a portion of the length of the second conduits. 3. Theplurality of second conduits can be freestanding within the interior ofthe first conduit, and can be free from physical contact with the firstconduit over the portion of the lengths of the second conduits.

The gas delivery system can also include a first gas within the firstgas source, wherein the first gas includes carbon monoxide, and a secondgas within the second gas source, wherein the second gas includes carbonmonoxide and an iron catalyst. The second end of the first conduit candefine a first orifice and second ends of the plurality of secondconduits can define a plurality of second orifices, wherein theplurality of second orifices have a circular shape.

In an implementation, the second end of the first conduit can define afirst orifice and seconds ends of the plurality of second conduits candefine a plurality of second orifices, wherein each second orifice ofthe plurality of second orifices has an oval shape. The gas deliverysystem can optionally include at least one thread, channel, or rifling,or combinations thereof, in at least one of the interior of the firstconduit and an interior of the second conduit, wherein the at least onethread, channel, or rifling is configured to impart a swirling motion toat least one of the first gas as it exits the first conduit and thesecond gas as it exits the second conduit.

The gas delivery system can further include a plurality of secondconduits each having a first end and a second end, wherein the secondend of the first conduit has a first diameter that delivers the firstgas through the first conduit into the reactor chamber at a firstvelocity. The second end of each second conduit of the plurality ofsecond conduits can include a second diameter that delivers the secondgas through each second conduit into the reactor chamber at a secondvelocity, and a ratio of the first velocity to the second velocity canbe from 0.1 to 1.1. An implementation of the gas delivery system mayinclude only one second conduit, wherein the second end of the firstconduit has a first diameter that delivers the first gas through thefirst conduit into the reactor chamber at a first velocity, the secondend of the second conduit has a second diameter that delivers the secondgas through the second conduit into the reactor chamber at a secondvelocity, and a ratio of the first velocity to the second velocity isfrom 0.1 to 1.1. Optionally, the second conduit is freestanding withinthe interior of the first conduit and is free from physical contact withthe first conduit over the portion of the length of the second conduit.

In another implementation, a gas delivery system includes a reactorchamber, a first conduit defining a first gas delivery port into thereactor chamber, and a second conduit defining a second gas deliveryport into the reactor chamber. In a cross section at the first gasdelivery port through the first conduit, the second conduit ispositioned entirely within the first gas delivery port defined by thefirst conduit, and the second conduit is free from physical contact withthe first conduit.

Optionally, the gas delivery system further includes a plurality ofsecond conduits defining a plurality of second gas delivery ports intothe reactor chamber wherein, in the cross section, the plurality ofsecond conduits are free from physical contact with the first conduit.Further optionally, in the cross section, each second conduit of theplurality of second conduits is free from physical contact with anyother second conduit. Additionally, in the cross section, the pluralityof second conduits can be freestanding and free from physical contactwith the first conduit.

The gas delivery system can further include a first gas source in fluidcommunication with first gas delivery port defined by the first conduitand a second gas source in fluid communication with the second gasdelivery port defined by the second conduit. In an optionalimplementation, the first gas delivery port defined by the first conduithas a first diameter that is designed to deliver a first gas from thefirst gas source into the reactor chamber at a first velocity, thesecond gas delivery port defined by the second conduit has a seconddiameter that is designed to deliver a second gas from the second gassource into the reactor chamber at a second velocity, and a ratio of thefirst velocity to the second velocity is from 0.1 to 1.1.

The gas delivery system can further include a first gas within the firstgas source, wherein the first gas includes carbon monoxide, and a secondgas within the second gas source, wherein the second gas includes carbonmonoxide and an iron catalyst.

In an optional implementation, the first conduit defines an interior ofthe first conduit, the second conduit defines an interior of the secondconduit, at least one of the first interior and the second interior hasat least one thread, channel, or rifling, or combinations thereof, andthe at least one thread, channel, or rifling is configured to impart aswirling motion to at least one of a first gas as it exits the first gasdelivery port and the second gas as it exits the second gas deliveryport. The gas delivery system can further include a thermal controldevice configured to maintain a thermal separation between the firstconduit and the second conduit, wherein the thermal control device hasat least one of a thermal insulation and a thermal coil.

In another implementation, a gas delivery system includes a reactorchamber, a first conduit defining a first gas delivery port into thereactor chamber, a plurality of second conduits having a plurality ofsecond gas delivery ports into the reactor chamber, wherein each secondconduit of the plurality of second conduits defines one second gasdelivery port of the plurality of second gas delivery ports. This gasdelivery system further includes a first gas source including a firstgas in fluid communication with the first conduit, wherein the first gasincludes carbon monoxide and a second gas source including a second gasin fluid communication with the second conduit, wherein the second gasincludes carbon monoxide gas and a catalyst. In a cross section at thefirst gas delivery port through the first conduit, the plurality ofsecond conduits are positioned entirely within the first gas deliveryport defined by the first conduit, each second conduit of the pluralityof second conduits is free from physical contact with the first conduit,and each second conduit of the plurality of second conduits is free fromphysical contact with any other second conduit.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in, and constitute apart of this specification, illustrate implementations of the presentteachings and, together with the description, serve to explain theprinciples of the disclosure. In the figures:

FIG. 1 is a perspective depiction of a gas delivery port for deliveringgases into a reaction vessel in accordance with an implementation of thepresent teachings.

FIG. 2 is a cross section of a reactor including the gas delivery portof FIG. 1.

FIG. 3 is an end view of the gas delivery port of FIG. 1.

FIG. 4 depicts the gas delivery port of FIG. 3 during delivery of afirst gas and a second gas.

FIG. 5 is an end view of a gas delivery port in accordance with animplementation of the present teachings.

FIG. 6 is an end view of a gas delivery port in accordance with animplementation of the present teachings.

FIG. 7 is an end view of a gas delivery port in accordance with animplementation of the present teachings.

FIG. 8 is an end view of a gas delivery port in accordance with animplementation of the present teachings.

FIG. 9 is a perspective depiction of a gas delivery port for deliveringgases into a reaction vessel.

FIG. 10 is a flow chart of a method in accordance with an implementationof the present teachings.

It should be noted that some details of the figures have been simplifiedand are drawn to facilitate understanding of the present teachingsrather than to maintain strict structural accuracy, detail, and scale.

DETAILED DESCRIPTION

Reference will now be made in detail to exemplary implementations of thepresent teachings, examples of which are illustrated in the accompanyingdrawings. Wherever possible, the same reference numbers will be usedthroughout the drawings to refer to the same or like parts.

Carbon nanotubes (CNTs), particularly high-purity, single-walled(SWCNTs) nanotubes, show great promise for the development of advancedmaterials. Mechanically, CNTs have high tensile elastic moduli and ademonstrated ability to improve material stiffness, strength, toughness,or vibrational damping resulting in a variety of applications.Electrically, CNTs have been shown to improve electrical conductivityand current density-functionalities and are increasingly used withinelectronic components and component packaging. CNTs have been shown topossess very high thermal conductivities, leading to applications asthermal interface materials and micro-scale heat exchange devices.Within the biotechnology sector, CNTs are being studied for a widevariety of applications from drug delivery to medical devices due to thechemical compatibility of CNTs with biological molecules. Often thebenefits are chirality-dependent, and this remains an active area ofresearch.

The presence of inclusions or other structural defects within thelattice structure of the CNT may significantly decrease the benefitsthat this nano-composite offers. The drive toward harnessing thepotential of this nanotechnology intersects with the manufacturabilityof suitable, plentiful CNTs.

One of the most common CNT production methods today is chemical vapordeposition (CVD). This process is well-suited for large scaleapplications, though multi-walled carbon nanotubes (MWCNTs) are thecheaper and more common form created. Unfortunately, compared to SWCNTs,MWCNTs are more prone to impurities or defects, thereby resulting in asignificant disparity between actual and predicted performance of theCNT-impregnated device regardless of application. The production ofhigher-purity SWCNTs is feasible with the CVD process, but both themonetary and temporal costs increase significantly over a comparablysized batch of MWCNTs.

An alternative to CVD-based SWCNT production is the High Pressure CarbonMonoxide (HiPCO) process. Though the HiPCO process shows promise information of SWCNTs, scaling up this process to form high-qualitymaterials in low-cost quantities suitable for an industrial productionenvironment has proved difficult. The HiPCO process includes the use ofthe exothermic Boudouard reaction, given by the equation:

CO_((g))+CO_((g+Fe Catalyst))

CO_(2(g))+C_((solid))

At the proper pressure and temperature and in the presence of an ironcatalyst, two parts of carbon monoxide react to yield one part carbondioxide and one part solid carbon. Provided the temperature of the mixedreactants is at least 500° C., the solid carbon will form SWCNTs atopeach iron cluster. Typically, laboratory-scale reactor operatingpressures are between 5 and 100 atmospheres, operating temperatures ofthe gas mixture is at least 800° C. and the total operating flow rate isapproximately 5 liters per minute (L/min), leading to gas velocities onthe order of centimeters per second. This slow gas velocity is necessaryto achieve the residence time for sufficient SWCNT growth to occurbefore the constituents reach the reactor outlet.

To achieve these conditions and deliver the iron catalyst, two separatestreams of inlet gas are delivered into the entrance region of thereactor and are combined via a free shear flow inside the reactorchamber within the mixing region. The boundary between mixing region andgrowth region is defined to be the point whereby the two separate gasstreams have combined into one uniform flow at a temperature sufficientto support the formation of SWCNTs. Gas stream 1 is pure CO at atemperature of 1200° C. Gas stream 2 is a mixture dominated by CO butwith trace concentrations of dispersed iron in the form of ironpentacarbonyl (Fe(CO)₅), all at a temperature between 25° C. and 200° C.The Fe(CO)₅ will decompose into free iron and five CO molecules once itstemperature reaches or exceeds 250° C., generating the iron necessary tocatalyze the reactants during the Boudouard reaction.

Since CNT growth does not initiate until the reactants reach atemperature of 500° C., there exists a temperature band between 250° C.and 500° C. referred herein as the “transition temperature range” wherethe Fe(CO)₅ decomposes without CNT growth. Free iron is unstable andtends to form compounds. Absent CNT growth at a temperature of less than500° C., the free iron particles will bond together thereby increasingthe size and mass of the iron clusters. At some point, the clustersbecome sufficiently large that CNT growth on the iron clusters cannot besupported. Further, the mass of the relatively large iron clusters mayresult in loss of the iron catalyst through precipitation of catalyticparticles such as the iron clusters out of the react gas, thus resultingin decreased catalysis of the reaction. Either of these outcomes leadsto fewer CNTs per batch and an increased CNT cost. Therefore, during CNTformation, reactant gases are mixed as rapidly and thoroughly aspossible, leading to rapid, uniform heating of the Fe(CO)₅ through thetransition temperature range.

In addition to chemical reactors, similar mixing problems arise often incombustion. Often, turbulence induction is employed to improve mixingtypically through the use of fluid jets. Unfortunately, when applied tothe HiPCO process, the eddies lead to rapid heating and cooling of theFe(CO)₅ across the transition temperature range, typically multipletimes, as the particles swirl through alternating regions of hot andcold gas which results in the formation of low-quality CNTs that may beadulterated with non-CNT forms of carbon.

As discussed above, the formation of quality SWCNTs in productionquantities using the Boudouard reaction is difficult due, at least inpart, to the critical temperatures at which the pure carbon monoxide(CO) gas stream (gas stream 1) and the iron-containing carbon monoxidegas stream (gas stream 2) must be delivered to the reactor. Whileformation of CNTs does not occur until the mixture of reactant gasreaches 500° C., decomposition of gas stream 2, particularly the ironcomponent such as Fe(CO)₅, occurs once the iron-containing carbonmonoxide is at 250° C. or above. Once decomposition of the ironcomponent begins to occur, larger iron clusters may form which resultsin decreased catalysis and a resulting decrease in the quantity ofSWCNTs formed. An attempt is therefore made to maintain theiron-containing reactant gas below 250° C., for example at about 200°C., prior to mixing with the pure CO gas stream. Ideally, once the tworeactants are mixed, the temperature of the iron-containing component isheated from the delivery temperature to the reaction temperature of atleast 500° C. as quickly as possible to reduce clustering of the ironduring decomposition within the 250° C. to 500° C. transitiontemperature range. The pure CO reactant may be delivered to the reactorat a temperature of 1200° C. or above so that once the reactants aremixed the iron-containing reactant is heated from the deliverytemperature (e.g., 200° C.) to the reaction temperature of 500° C. orabove as quickly as possible.

An implementation of the present teachings provides a gas deliverysystem and method used to deliver and mix reactant gases within areactor. A first reactant is maintained at a first temperature (forexample, 1200° C.) and the second reactant is maintained at a secondtemperature that is lower than the first temperature (for example, 200°C.). The gas delivery system delivers the reactant gases at an increasedsurface area, thereby increasing the likelihood that the reactants willencounter each other to improve their mixing and the chemical reactionrate compared to some prior reactor mixing systems. Transfer of thermalenergy from the first reactant to the second reactant may therefore bemore efficient such that an entirety of the second reactant is broughtto a desired reaction temperature (for example, 500° C. or above) morequickly than realized with prior gas delivery systems. As such, thereactant gases may be introduced into the reactor at reduced velocitiescompared to some prior systems, thereby reducing turbulence andassociated negative effects on reactant mixed gas temperature.

FIG. 1 is a schematic perspective depiction of a portion of a gasdelivery system 100, and FIG. 2 is a sectional side view of the gasdelivery system 100 that is part of a reactor 250 such as a HighPressure Carbon Monoxide (HiPCO) reactor, in accordance with animplementation of the present teachings. This exemplary implementationis described with reference to delivering two different gas streams intoa reactor chamber 102 or other reaction vessel 102. The reactor chamber102 may be defined by one or more reactor chamber walls 104, althoughother configurations are contemplated. In this implementation, the gasdelivery system 100 includes a gas delivery port 106 for introducing ordelivering two or more gases into the reactor chamber 102 includes aplurality of chamber gas inlets into the reactor chamber 102, includinga first orifice or inlet 108 for delivering a first gas, and a pluralityof second orifices or inlets 110 for delivering a second gas, into thereactor chamber 102. In this implementation, six second inlets 110 aredepicted. The present teachings are discussed herein with reference to aplurality of second inlets 110, although a gas delivery port 106 mayinclude only one second inlet 110, or two or more second inlets 110. Thegas delivery port 106 may be flush with the reactor chamber wall 104 asdepicted, or one or more portions of the gas delivery port 106 mayextend into the reactor chamber 102.

The first inlet or orifice 108 may be disposed at a second end 200 of afirst pipe, tube, line, or conduit (hereinafter, collectively “conduit”)112. A first end 202 of the first conduit 112 may be in fluidcommunication with, and supplied by, a first gas source 204 having afirst gas 205. The plurality of second inlets 110 may each be disposedat a second end 206 of one of a plurality of second conduits 114. Afirst end 208 of each second conduit 114 may be in fluid communicationwith, and supplied by, a second gas source 210 having a second gas 211.The gas sources 204, 210 may each be one or more of a supply line, a gasstorage tank, or another type of gas source.

The first conduit 112 and each of the second conduits 114 may bemanufactured from a material such as stainless steel or another suitablematerial, or suitable combination of materials, that provide sufficientstrength and rigidity and are chemically inert, or acceptably reactivewith, the reactant fluids they transport.

As depicted in FIGS. 1 and 2, each second conduit 114 has a lengthbetween the first end 208 and the second end 206 of each second conduit114. The first conduit 112 completely encircles the plurality of secondconduits 114 through at least a portion “L” of the conduit lengths. Theportion “L” may be positioned between the first and second gas sources204, 210 and the gas delivery port 106 (e.g., between the first end 208and the second end 206). As depicted in FIG. 1, each second conduit 114may be spaced from adjacent second conduits 114 such that the first gas205 may, in a cross section, surround each second conduit 114 as well asthe second gas 211 within each second conduit 114.

Prior to delivery of the first gas 205 within the first gas source 204and the second gas 211 within the second gas source 210, the first gas205 and the second gas 211 may be heated or cooled to a desiredtemperature. For example, to form SWCNTs within the reactor chamber 102,the first gas (pure CO gas) 205 within the first gas source 204 may beheated to about 1200° C., while the second gas (CO+Fe(CO)₅ gas) 211within the second gas source 210 is heated to about 200° C., or to atemperature less than the decomposition temperature of the Fe(CO)₅(i.e., <250° C.). The temperatures may be selected so that once thegases 205, 211 are simultaneously delivered to the reactor chamber 102,the second gas 211 is rapidly heated through the transition temperaturerange of between 250° C. and 500° C. to a reaction temperature of 500°C. or above.

FIG. 3 is an end view of the gas delivery port 106 including the firstconduit 112 and the plurality of second conduits 114 that extend throughthe first conduit 112. FIG. 4 depicts the gas delivery port 106 of FIG.3 during an initial delivery of the first gas 205 from the first orifice108 at the second end 200 of the first conduit 112 and the second gas211 from each second orifice 110 at the second end 206 of each of theplurality of second conduits 114. As depicted, during delivery of thegases 205, 211 from the gas delivery port 106, the stream of the firstgas 205, at least in a cross section, encircles each stream of thesecond gas 211. This increases the area of contact between the gases205, 211 during delivery into the reactor chamber 102 compared to asystem that delivers two separate and discrete gas streams.

In an implementation to form SWCNTs, pure CO gas may be delivered intothe reactor chamber 102 through the first conduit 112 at a temperatureof from about 800° C. to about 1600° C., for example about 1200° C.Simultaneously, CO gas doped with a catalyst such as iron, for example,compounded in the form of Fe(CO)₅, may be delivered into the reactorchamber 102 through the plurality of second conduits 114 at atemperature of below 250° C., for example, from about 30° C. to about240° C., or from about 150° C. to about 220° C., for example about 200°C. It will be understood that the “pure CO gas” may include otherchemically inert materials, for example, an inert gas used to adjust theconcentration of the CO gas within the first gas stream, unlessotherwise specified. In an implementation, the CO portion of the secondgas stream may include from about 95 percent by volume (volume %) toabout 99.9 volume % CO gas and from about 0.1 volume % to about 5 volume% Fe(CO)₅ as a solid suspended within the CO gas.

Prior designs of HiPCO reactors to form high-quality SWCNTs haveheretofore been laboratory scale. Scaling of HiPCO reactors forproduction quantities of SWCNTs has been limited or not possible, atleast in part, because maintaining proper temperatures of reactant gaseshas not been possible with prior HiPCO reactor designs. Further, priorattempts at upscaling HiPCO reactor designs have not been successful, atleast in part, because delivering reactant gases into a reactor chamberhas been inefficient and results in poor mixing of reactant gases. Forproper mixing of reactant gases to form high-quality SWCNTs using theBoudouard equation, the velocities of the two reactant gases must beproperly controlled as they are delivered into the reactor chamber.Further, the two reactant gases must come into physical contact witheach other quickly to allow the chemical reaction to occur at the propertemperature. An aspect of the present teachings may be used to scale up(or scale down) a HiPCO reactor to form production quantities (or samplequantities) of high-quality SWCNTs as described below.

FIG. 5 depicts a fluid delivery port 500 in accordance with animplementation of the present teachings. This fluid delivery port 500includes a first conduit 502 having a first orifice 504 for deliveringthe first gas stream (e.g., for delivering relatively hot, pure CO at atemperature of about 1200° C.) and only one second conduit 506 having asecond orifice 508 for delivering the second gas stream (e.g., fordelivering relatively cold CO+Fe catalyst at a temperature of about 200°C.). The value “D₁” is the diameter of the first orifice 504, while thevalue “D₂” is the diameter of the second orifice 508. For a givendelivery pressure of the first gas, the value of D₁ will control thevelocity at which the first gas is delivered into the reactor chamberthrough the first orifice 504. Similarly, for a given delivery pressureof the second gas, the value of D₂ will control the velocity at whichthe second gas is delivered into the reactor chamber through the secondorifice 508. The ratio of D₁/D₂ is dependent on the mass flow rates ofeach inlet gas, but is selected or designed to achieve a particularratio of the velocity of the hot gas stream (e.g., pure CO gas) to thevelocity of the cold gas stream (e.g., CO mixed with the iron catalyst).In this implementation, D₁ and D₂ are selected such that a ratio of thevelocity of the first gas to a velocity of the second gas (i.e., a ratioof the velocity of the hot gas stream to the cold gas stream, or“D₁/D₂”) delivered into the reactor chamber from the respective orifices(or “D₁/D₂”) is from about 0.1 to about 1.1, or from about 0.1 to about1.0, or from about 0.3 to about 1.0. In another aspect, a first crosssectional area provided by the first orifice 504 and a second crosssectional area provided by the second orifice 508, for given deliverypressures of the first gas stream and the second gas stream, result inthe ratio of the velocity of the first gas stream to the velocity of thesecond gas stream being from about 0.1 to about 1.1, or one of the othervalues as described above. Controlling the velocities of each of thereactant gas streams, and thus the ratio D₁/D₂, allows for a controlledmixing of reactant gases while reducing or eliminating turbulence andeddies. Turbulence and eddies, as described above, can result in rapidheating and cooling of the iron-containing gas stream(s) and, in turn,form low-quality CNTs that may be adulterated with non-CNT forms ofcarbon.

The value of D₁/D₂, where D₁ is the velocity of the first gas stream(pure CO) and D₂ is the velocity of the second gas stream (CO+Fecatalyst, for example, Fe(CO)₅), is referred to herein as the “gasvelocity ratio.” Further, the depiction of FIG. 5 is a particular gasflow path described herein as a “unit cell” as it includes only onesecond orifice 508 (or second diameter D₂) for the for each diameter D₁.While diameter D₁ of FIG. 5 is provided by an actual structure (i.e.,the first conduit 502), D₁ may also be a theoretical distance or spacingused to design a reactor that is scaled up (or scaled down) to have anincreased (or decreased) SWCNT output.

The principle of the gas velocity ratio and the unit cell may be used todesign a HiPCO reactor having a desired output of high-quality SWCNTs.In particular, the HiPCO reactor may be scaled up and designed for largequantities (i.e., production quantities) of SWCNTs. In contrast to thefluid delivery port 500 of FIG. 5 that includes a single second conduit506 and a single second orifice 508 for delivering the second gas stream(i.e., a single unit cell), FIG. 6, for purposes of explanation, depictsa fluid delivery port 600 having seven second conduits 602 and thusseven second orifices 604 (i.e., seven unit cells) that deliver thesecond gas into a reactor chamber. A fluid delivery port may include anynumber of second conduits and second orifices, for example, from one to10, or more than 10. FIG. 6 further depicts a first conduit 606 having afirst orifice 608 that delivers the first gas into the reactor chamber,wherein each of the second conduits 602 are positioned within theinterior of the first conduit 606. In this implementation, the boundaryof the flow path of the first gas defined within each iteration of D₁ isa theoretical boundary. While the actual sizes of D₁ and D₂ may change,the sizes of D₁ and D₂ are selected to maintain the gas velocity ratiodescribed above. In theory, the diameter of the first conduit 606 andthe plurality of second conduits 602 may be any size, as long as thesize of the unit cell results in the gas velocity ratio within theselected ranges described above. Typically, the dimension D₂ of thesecond conduits 602 may be in the range of 1 millimeter (mm) to 20 mm.It will be appreciated that only certain combinations of D₁ and D₂dimensions maintain the gas velocity ratio and result in sufficientreactant gas mixing. The overall reactor size and the arrangementpattern of unit cell flow paths simplifies down to a two dimensionalpacking calculation, and may be determined by one of ordinary skill inthe art.

As depicted in FIG. 6, each of the unit cells including D₁ and D₂ fitwithin the circumference of the first conduit 606. In FIG. 6, there isno overlap between adjacent unit cells. D₁ of each unit cell is tangentwith D₁ of two or more adjacent unit cells. Each unit cell at aperiphery of the fluid delivery port 600 is tangent with the firstconduit 606.

Thus, in contrast to prior fluid delivery port and reactor designs, thepresent teachings allow scalability of the reactor provided the reactoris designed such that the ratio of D₁/D₂ provides the described gasvelocity ratio. This scalability of a reactor according to the presentteachings, particular up scaling to increase throughput, increasesproduction and drives down the cost of materials.

The shapes of the first orifice 108 of the first conduit 112 theplurality of second orifices 110 of the plurality of second conduits 114may have a circular shape as depicted in FIG. 3. In some uses, othershapes may be used to tailor the fluid dynamics of each gas stream as itis delivered into the reactor chamber 102 for a particular use. Forexample, FIG. 7 depicts a gas delivery port 700 where a first orifice702 formed by a second end of a first conduit 704 has a circular shape,where a second end of each of a plurality of second conduits 706 formsan oval-shaped orifice 708. Oval-shaped orifices 708 may functiondifferently from the circular orifices 110 of FIG. 3 in that the flowpatterns may result in increased entrainment, and therefore improvedfluid mixing, without significant recirculation patterns present intraditional turbulent mixing apparatuses. These features, combined withthe resulting increased surface areas, may reduce temperaturenon-uniformity and contribute to increased catalyst dispersion.

As discussed above, in an implementation, it may be advantageous ornecessary for a given chemical reaction to maintain the gas in theplurality of second conduits at a different temperature from the gas inthe first conduit until the gases are introduced into the reactorchamber 102. FIG. 8 depicts a structure similar to that of FIG. 3, andfurther including one or more thermal control devices 800 configured tomaintain thermal separation of the gases during transport from the gassources 204, 210 (FIG. 2) to the reactor chamber 102. The thermalcontrol device 800 may be a passive thermal control device, for example,a thermal insulation, such as a natural or synthetic insulation, thatencases each of the plurality of second conduits 114. In anotherimplementation, the thermal control device 800 may be an active thermalcontrol device, for example, a thermal coil such as a heating coil or acooling coil that is wrapped or otherwise disposed on, around, or neareach of the plurality of second conduits 114. In another aspect, thethermal control device 800 may include both a thermal insulation and athermal coil. The thermal control device 800 may be positioned betweenthe exterior of each second conduit 114 and the first gas within thefirst conduit 112. In another aspect, the thermal control device 800 maybe positioned between the first gas 205 within the first conduit 112 andthe second gas 211 within the plurality of second conduits 114.

In various implementations such as those depicted in FIGS. 1 and 2, theinterior surfaces of the first conduit 112 and/or the one or more secondconduits 114 may be smooth. In various other implementations such asthat depicted in FIG. 9, a gas delivery port 900 may be configured tocustomize fluid flow dynamics of the gases as they are introduced intothe reactor chamber 102 (FIG. 1), such that either or both the first gas205 and the second gas 211 exit the fluid delivery port 900 with agentle swirling motion that enhances the mixing of the reactant gases toincrease the reactions occurring between molecules of the reactantgases. The gas delivery port 900 of FIG. 9 depicts a first conduit 902having a first orifice 904 and a plurality of second conduits 906 eachhaving a second orifice 908. The plurality of second conduits 906 arepositioned within an interior of the first conduit 902.

In FIG. 9, the second conduits 906 may include one or more threads,channels, or rifling 910 (hereinafter, threads), or combinationsthereof, that extend through at least an end of the second conduits 906to impart a directionality to the second gas as it exits the fluiddelivery port 900. In an implementation, the threads 910 may extendthrough an entirety of the length “L” (FIG. 2) of the second conduits906. In another implementation, the threads 910 may be formed only atthe second end 206 (FIG. 2) of the second conduits 906. The threads 910are formed with a length sufficient to impart a gentle swirling motionto the second gas as it exits each second orifice 908. The threads 910of each second conduit 906 may be formed to impart one of a clockwiseswirling motion or a counterclockwise swirling motion of the second gasas it exits each second orifice 908. In an implementation, the threads910 of one or more of the second conduits 906 may be formed to impart aclockwise swirling motion of the second gas, while the threads 910 ofone or more of the second conduits 906 may be formed to impart acounterclockwise swirling motion to the second gas. In animplementation, one or more of the second conduits 906 may includethreads 910, while one or more second conduits 906 may not includethreads. The threads 910 may be formed as raised threads that protrudefrom internal sidewalls of the second conduit 906 into an interior ofthe second conduit 906, or they may be formed as channels that extendinto the internal sidewalls of the second conduit 906.

In FIG. 9, the first conduit 902 may also include one or more channels,threads, or rifling 912 (hereinafter, threads 912), or combinationsthereof, that extend through at least an end of the first conduit 902 toimpart a directionality to the first gas as it exits the fluid deliveryport 900. In an implementation, the threads 912 may extend through anentirety of the length “L” (FIG. 2) of the first conduits 902. Inanother implementation, the threads 912 may be formed only at the secondend 200 (FIG. 2) of the first conduits 902. The threads 912 are formedwith a length sufficient to impart a gentle swirling motion to the firstgas as it exits the first orifice 904. The threads 912 of the firstconduit 902 may be formed to impart one of a clockwise swirling motionor a counterclockwise swirling motion to the first gas as it exits thefirst orifice 904. The threads 912 may be formed as raised threads thatprotrude from internal sidewalls of the first conduit 902 into aninterior of the first conduit 902, or they may be formed as channelsthat extend into the internal sidewalls of the first conduit 902. Thethreads 912 of the first conduit 902 may be referred to as “firstthreads” while the threads 910 of the second conduits 906 may bereferred to as “second threads.”

As described above, the optional first threads 912 and the optionalsecond threads 910 may be used to impart a clockwise and/orcounterclockwise gentle swirling motion to the first gas 205 and/or thesecond gas 211 respectively, thereby imparting a vortex, current, ordirectionality to the first gas 205 and/or the second gas 211respectively. The directionality of the first threads 912 of one or moreof the second conduits 906 may be the same or different than thedirectionality of the second threads 910 of the first conduit 902. Thedirectionality may improve physical contact or reaction of the first gas205 with the second gas 211.

FIG. 10 is a flow chart depicting a method in accordance with animplementation of the present teachings. For purposes of explanation,the method of FIG. 10 is described with reference to FIGS. 1-6, althoughother structures for performing the method of FIG. 10 are contemplated.As described at 1002, a first gas 205 may be transported from a firstgas source 204 into a first end 202 of a first conduit 112. At 1004, asecond gas 211 from a second gas source 210 may be transported into afirst end 208 of at least one second conduit 114. A length “L” of thesecond conduit 114, which may be a portion of an entire length of thesecond conduit 114, is positioned within an interior of the firstconduit 112. Through length L, the at least one second conduit 114 maybe freestanding and free from physical contact with the first conduit112 as depicted, for example, at FIG. 2.

At 1006, the first gas 205 may be transported through the first conduit112 while the second gas 211 is simultaneously transported through theat least one second conduit 114 to a gas delivery port 106 at a secondend 200 of the first conduit 112 and a second end 206 of the at leastone second conduit 114. Next, with reference to 1008, the first gas 205and the second gas 211 may be simultaneously introduced into a reactorchamber 102 of a reactor 250 or another volume through the gas deliveryport 106.

In an implementation using the Boudouard reaction, the gases may beintroduced at a relatively low pressure compared to conventional methodsof formation. As discussed above, introducing the reactants into thereactor chamber at a reduced pressure may be advantageous because highturbulence, when applied to a HiPCO process, creates eddies that maylead to rapid heating and cooling of the Fe(CO)₅ across the transitiontemperature range, typically multiple times, as the particles swirlthrough alternating regions of hot and cold gas. This, in turn, mayresult in the formation of low-quality SWCNTs that may be adulteratedwith non-CNT forms of carbon.

As the first gas 205 and the second gas 211 are introduced into thereactor chamber 102, they are mixed as described at 910. As the firstgas 205 and the second gas 211 mix, they may chemically react within thereactor chamber 102 or other reaction vessel or volume as described at912. Additional processing of the reactant resulting from the mixing ofthe first gas 205 and the second gas 211 may continue.

FIGS. 1-9 depict a single gas delivery port that introduces gases into avolume such as a chamber 102 of a reactor 250. It will be appreciatedthat a plurality of gas delivery ports may be employed to simultaneouslyintroduce gases into a volume such as a reactor chamber 102 at aplurality of different locations within the volume.

In an implementation, size, capacity, and/or throughput of the firstconduit and the plurality of second conduits may be based, at least inpart, on the stoichiometry of the chemical equation that is being usedwith the gas delivery system. In the Boudouard equation above, one moleof pure CO gas is needed for every mole of CO gas doped with iron. Inthe FIG. 3 depiction, the pure CO gas may be delivered through the firstinlet 108 while the iron-doped CO gas may be delivered through theplurality of second inlets 110. In this implementation, a crosssectional area of the first inlet 108 may be equal to, or approximatelyequal to, the sum of the cross sectional areas of each of the pluralityof second inlets 110. The cross sectional areas may vary with otherfactors independent of the stoichiometry, for example, if one of thereactants is mixed with an inert diluent.

Thus an implementation of the present teachings may be used to providefor an improved chemical reaction by allowing for improved mixing ofreactants. In an implementation, a larger surface area of the reactantscome in contact to provide for improved mixing. The plurality of secondconduits that deliver a plurality of smaller gas streams within a largergas stream provides a laminar flow of gases into a volume such as areactor chamber. Introduction of gases into the volume at a lowerpressure may allow for decreased turbulence and an improved temperatureprofile of the reagents during formation of a product. In the example ofthe Boudouard reaction, improved mixing may yield a higher quantityand/or weight of SWCNTs for a given molar quantity of reactants. Amanufacturing system and process that uses an implementation of thepresent teachings may be more suitable for producing productionquantities of SWCNTs than prior systems and methods of formation.

It will be appreciated that a system and method in accordance with animplementation of the present teachings may include structures or methodacts that, for simplicity, have not been depicted in the figures, andthat various depicted structures or method acts may be removed ormodified.

Notwithstanding that the numerical ranges and parameters setting forththe broad scope of the present teachings are approximations, thenumerical values set forth in the specific examples are reported asprecisely as possible. Any numerical value, however, inherently containscertain errors necessarily resulting from the standard deviation foundin their respective testing measurements. Moreover, all ranges disclosedherein are to be understood to encompass any and all sub-ranges subsumedtherein. For example, a range of “less than 10” can include any and allsub-ranges between (and including) the minimum value of zero and themaximum value of 10, that is, any and all sub-ranges having a minimumvalue of equal to or greater than zero and a maximum value of equal toor less than 10, e.g., 1 to 5. In certain cases, the numerical values asstated for the parameter can take on negative values. In this case, theexample value of range stated as “less than 10” can assume negativevalues, e.g. −1, −2, −3, −10, −20, −30, etc.

While the present teachings have been illustrated with respect to one ormore implementations, alterations and/or modifications can be made tothe illustrated examples without departing from the spirit and scope ofthe appended claims. For example, it will be appreciated that while theprocess is described as a series of acts or events, the presentteachings are not limited by the ordering of such acts or events. Someacts may occur in different orders and/or concurrently with other actsor events apart from those described herein. Also, not all processstages may be required to implement a methodology in accordance with oneor more aspects or implementations of the present teachings. It will beappreciated that structural components and/or processing stages can beadded or existing structural components and/or processing stages can beremoved or modified. Further, one or more of the acts depicted hereinmay be carried out in one or more separate acts and/or phases.Furthermore, to the extent that the terms “including,” “includes,”“having,” “has,” “with,” or variants thereof are used in either thedetailed description and the claims, such terms are intended to beinclusive in a manner similar to the term “comprising.” The term “atleast one of” is used to mean one or more of the listed items can beselected. As used herein, the term “one or more of” with respect to alisting of items such as, for example, A and B, means A alone, B alone,or A and B. The term “at least one of” is used to mean one or more ofthe listed items can be selected. Further, in the discussion and claimsherein, the term “on” used with respect to two materials, one “on” theother, means at least some contact between the materials, while “over”means the materials are in proximity, but possibly with one or moreadditional intervening materials such that contact is possible but notrequired. Neither “on” nor “over” implies any directionality as usedherein. The term “conformal” describes a coating material in whichangles of the underlying material are preserved by the conformalmaterial. The term “about” indicates that the value listed may besomewhat altered, as long as the alteration does not result innonconformance of the process or structure to the illustratedimplementation. Finally, “exemplary” indicates the description is usedas an example, rather than implying that it is an ideal. Otherimplementations of the present teachings will be apparent to thoseskilled in the art from consideration of the specification and practiceof the disclosure herein. It is intended that the specification andexamples be considered as exemplary only, with a true scope and spiritof the present teachings being indicated by the following claims.

Terms of relative position as used in this application are defined basedon a plane parallel to the conventional plane or working surface of aworkpiece, regardless of the orientation of the workpiece. The term“horizontal” or “lateral” as used in this application is defined as aplane parallel to the conventional plane or working surface of aworkpiece, regardless of the orientation of the workpiece. The term“vertical” refers to a direction perpendicular to the horizontal. Termssuch as “on,” “side” (as in “sidewall”), “higher,” “lower,” “over,”“top,” and “under” are defined with respect to the conventional plane orworking surface being on the top surface of the workpiece, regardless ofthe orientation of the workpiece.

1. A gas delivery system, comprising: a first conduit having a first endand a second end, wherein the first end of the first conduit is attachedto a first gas source; a second conduit having a first end and a secondend, wherein: the first end of the second conduit is attached to asecond gas source; and the second conduit has a length and is positionedentirely within an interior of the first conduit over at least a portionof the length; and a gas delivery port, comprising: the second end ofthe first conduit; and the second end of the second conduit, wherein thegas delivery port is configured to deliver a first gas within the firstgas source through the first conduit into a reactor chamber and a secondgas within the second gas source through the second conduit to thereactor chamber.
 2. The gas delivery system of claim 1, furthercomprising a plurality of second conduits each having a length, and thelength of each second conduit is positioned entirely within the interiorof the first conduit over at least a portion of the length of the secondconduits.
 3. The gas delivery system of claim 2, wherein the pluralityof second conduits are freestanding within the interior of the firstconduit and are free from physical contact with the first conduit overthe portion of the lengths of the second conduits.
 4. The gas deliverysystem of claim 2, further comprising: a first gas within the first gassource, wherein the first gas comprises carbon monoxide; and a secondgas within the second gas source, wherein the second gas comprisescarbon monoxide and an iron catalyst.
 5. The gas delivery system ofclaim 2, wherein: the second end of the first conduit defines a firstorifice; and second ends of the plurality of second conduits define aplurality of second orifices, wherein the plurality of second orificeshave a circular shape.
 6. The gas delivery system of claim 2, wherein:the second end of the first conduit defines a first orifice; and secondsends of the plurality of second conduits define a plurality of secondorifices, wherein each second orifice of the plurality of secondorifices has an oval shape.
 7. The gas delivery system of claim 1,further comprising at least one thread, channel, or rifling, orcombinations thereof, in at least one of the interior of the firstconduit and an interior of the second conduit, wherein the at least onethread, channel, or rifling is configured to impart a swirling motion toat least one of the first gas as it exits the first conduit and thesecond gas as it exits the second conduit.
 8. The gas delivery system ofclaim 1 further comprising a plurality of second conduits each having afirst end and a second end, wherein: the second end of the first conduithas a first diameter that delivers the first gas through the firstconduit into the reactor chamber at a first velocity; the second end ofeach second conduit of the plurality of second conduits comprises asecond diameter that delivers the second gas through each second conduitinto the reactor chamber at a second velocity; and a ratio of the firstvelocity to the second velocity is from 0.1 to 1.1.
 9. The gas deliverysystem of claim 1 further comprising only one second conduit, wherein:the second end of the first conduit has a first diameter that deliversthe first gas through the first conduit into the reactor chamber at afirst velocity; the second end of the second conduit comprises a seconddiameter that delivers the second gas through the second conduit intothe reactor chamber at a second velocity; and a ratio of the firstvelocity to the second velocity is from 0.1 to 1.1.
 10. The gas deliverysystem of claim 1, wherein the second conduit is freestanding within theinterior of the first conduit and is free from physical contact with thefirst conduit over the portion of the length of the second conduit. 11.A gas delivery system, comprising: a reactor chamber; a first conduitdefining a first gas delivery port into the reactor chamber; and asecond conduit defining a second gas delivery port into the reactorchamber; wherein, in a cross section at the first gas delivery portthrough the first conduit: the second conduit is positioned entirelywithin the first gas delivery port defined by the first conduit; and thesecond conduit is free from physical contact with the first conduit. 12.The gas delivery system of claim 11, further comprising a plurality ofsecond conduits defining a plurality of second gas delivery ports intothe reactor chamber wherein, in the cross section, the plurality ofsecond conduits are free from physical contact with the first conduit.13. The gas delivery system of claim 12 wherein, in the cross section,each second conduit of the plurality of second conduits is free fromphysical contact with any other second conduit.
 14. The gas deliverysystem of claim 12 wherein, in the cross section, the plurality ofsecond conduits are freestanding and free from physical contact with thefirst conduit.
 15. The gas delivery system of claim 11, furthercomprising: a first gas source in fluid communication with first gasdelivery port defined by the first conduit; and a second gas source influid communication with the second gas delivery port defined by thesecond conduit.
 16. The gas delivery system of claim 15, wherein: thefirst gas delivery port defined by the first conduit has a firstdiameter that is designed to deliver a first gas from the first gassource into the reactor chamber at a first velocity; the second gasdelivery port defined by the second conduit has a second diameter thatis designed to deliver a second gas from the second gas source into thereactor chamber at a second velocity; and a ratio of the first velocityto the second velocity is from 0.1 to 1.1.
 17. The gas delivery systemof claim 15, further comprising: a first gas within the first gassource, wherein the first gas comprises carbon monoxide; and a secondgas within the second gas source, wherein the second gas comprisescarbon monoxide and an iron catalyst.
 18. The gas delivery system ofclaim 11, wherein: the first conduit defines an interior of the firstconduit; the second conduit defines an interior of the second conduit;at least one of the first interior and the second interior comprises atleast one thread, channel, or rifling, or combinations thereof; and theat least one thread, channel, or rifling is configured to impart aswirling motion to at least one of a first gas as it exits the first gasdelivery port and the second gas as it exits the second gas deliveryport.
 19. The gas delivery system of claim 11, further comprising athermal control device configured to maintain a thermal separationbetween the first conduit and the second conduit, wherein the thermalcontrol device comprises at least one of a thermal insulation and athermal coil.
 20. A gas delivery system, comprising: a reactor chamber;a first conduit defining a first gas delivery port into the reactorchamber; a plurality of second conduits comprising a plurality of secondgas delivery ports into the reactor chamber, wherein each second conduitof the plurality of second conduits defines one second gas delivery portof the plurality of second gas delivery ports; a first gas sourcecomprising a first gas in fluid communication with the first conduit,wherein the first gas comprises carbon monoxide; and a second gas sourcecomprising a second gas in fluid communication with the second conduit,wherein the second gas comprises carbon monoxide gas and a catalyst;wherein, in a cross section at the first gas delivery port through thefirst conduit: the plurality of second conduits are positioned entirelywithin the first gas delivery port defined by the first conduit; eachsecond conduit of the plurality of second conduits is free from physicalcontact with the first conduit; and each second conduit of the pluralityof second conduits is free from physical contact with any other secondconduit.